Double pressure compressed air electric apparatus having an air drying device

ABSTRACT

Double pressure compressed air electric apparatus such as an air-blast circuit interrupter having a high-pressure tank and a low-pressure (exhaust) tank whereby the low-pressure is greater than the atmospheric pressure under normal operating conditions. A compressor taking air from the low-pressure tank supplies highpressure air to the high-pressure tank. A three-way valve cooperating with an air-drying device causes said compressor to take air from the atmosphere in case the low-pressure drops to a dangerous value under the influence of a leakage in the system. The additional quantity of air taken from the atmosphere is dried by the air-drying device.

Henry et al;

United States Patent} '6 I [151 3,701,867 451 Oct. 31, 1972 [54] DOUBLEPRESSURE COMPRESSED AIR ELECTRIC APPARATUS HAVING AN AIR DRYING DEVICE tf Inventors: Jean Claude Henry; GerardfBillon, both of Grenoble, Francej A Assignee: Merlin Gerin, Anonyme,

Grenoble, France Filed: Feb. 26, 1971 .Appl; No.2 119,255

[so] Foreign Application Priority pm March 4, 1970 Fr-611..-....'.70o7s17.

[561 References Cited UNITED sTATEs PATENTS us. (:I.....'.. .2o0/14s j2001148 B: .Int.(1l.., .I..H01h 33/57; j Field 6: Search .200/148 12,148G, 148R FOREIGN PATENTS oR APPLICATIONS 1 696,066 10/1964 Canada..200/l48E 1,178,925 r 5/1961 Germany ..200/148R Primary Examiner-RobertS. Macon v Attorney-Stevens, Davis, Miller 8; Mosher 571' ABSTRACTDouble pressure compressed air electric I apparatus such as an air-blastcircuit interrupter having a highpressure tank and a low-pressure(exhaust) tank whereby the low-pressure is greater than the atmosphericpressure under normal operating conditions.JA compressor taking air fromthe low-pressure tank supplies high-pressure air to the high-pressuretank. Athree-way valve cooperating with .an-air-drying device causessaid compressor to take air from the atmosphere in case the low-pressuredrops to :1 dangerous value under the influence of a leakage in the2,550,886 5/1951 Th6mps6n,........ .2o0/14sEX 3,566,062 2/1971 Meier";.L.200/148E system. The additional quantity of air taken from theatmosphere is dried by the air-drying device.

3 Claims, Drawing Figures PATENTKDDBIM IQR 3.701.867-

sum 1 OF 2 PATENTED nm 3 1 m2 SHEET 2 BF 2 all I I1 DOUBLE COMPRESSEDAIR ELECTRIC APPARATUS HAVING AN AIR DRYING I on air-blast circuitinterrupters is well known,-and particularly the danger of condensationon the insulating walls, which causes flash-over. Consequently, theconventional compressor groups for compressed air circuit interruptersmust be equipped with water separators and/or air drying devices whichconstitute large and bulky systems which must treat'large quantities ofair to be'evacuated into the atmosphere .after only a single use. 1

- It is well known that the drying of the air is readily effected bycontacting itlwithab'sorben t products, but thesedevices can bedesignedonly for the treatment of small quantities-of air since the absorptioncapacity of According to the invention, means are provided to sure tankwhereby an air-drying device dries the air these products islimited.The-frequentreplacement or regeneration of the absorbent products areincompatible with the. normal maintenance .of electrical app'aratusunder economical conditions.

The applicant, in its copending patent application filed on Oct. 16,1969, under Ser. No; 867.012, has disclosed a device of the typementioned in which the normal pressure prevailing in thelow-pressure'enclosure is close to atmospheric pressure, an inlet valvecausing atmospheric air to enter said enclosure when the pressuretherein drops below a predetermined value as the result of a leakage ofcompressed air towards the outside. This system permits the circuitinterrupter to operate normally in closed cycle with a quantity of airwhich has been dried once and for all,- an additional quantity i of airbeing introduced from the atmosphere" in a limited way only in the eventof a leakage from the system towards the outside. device for therecovery of dry air and circulation in a substantially closed cyclewhich comprises a drier provides a satisfactory solution by decreasingthe use of the absorbent material. As a matter of fact, the feed aircontinuously passes through the drying deviceof absorbent filterinserted in the circulation system, but once dry it deposits thereinmerely traces of moisture-resulting from possible slight leaks which arecompensated for by an addition of ambient air. The filter retains itsabsorbent properties longer the more limited are the quantities ofambient air introduced into the circulation system.

This system has given full satisfaction in practice but cannot be usedin case the low pressure value is substantially higher than atmosphericpressure, such as of the order of 4 bars.

thus introduced in the substantially closed cycle y m Other advantagesand features will become evident from the following description of twoembodiments of the invention which are shown schematically, partially inaxial section, in the accompanying drawings by way of illustration andnot of limitation.

The example selected consists of a compressed-air circuit interrupterwhich operates in closed cycle, but

'the invention may naturally find other applications inany electricapparatus utilizing two compressed air pressures and subject to leakswhich make aninterrnittent addition of moist outer air necessary.

In FIG. 1, a compressed-air circuit interrupter has twoarc-extinguishing chambers 10, 12 borne by a hollow support insulator 14 secured at its lower end to a low-pressure, enclosure or tank 16 whichis located in a zone of ground potential in such a manner that theinside of the insulator 14 communicates normallyhermetically with thetank 16. An insulating conduit 18 extending the insulator 14 connectsthe highand low-potential zones and feeds the chambers I0, 12 withhighpressurized air. Depending on the type of circuit interrupter used,the air forwarded by the conduit 18 can feed auxiliary high-pressuretanks located in the region of high potential or directly feed arc blastdevices or pneumatic control devices for the contacts (not shown)located in the chambers.

Within the low-pressure housing or tank 16 there is arrange a Compressor20 which, via a conduit 24, in

' which an air-drying filter 26 is also inserted, feeds a high-pressuretank 28, which is also housed within the low-pressure tank 16.Theconduit'lS is connected to the tank 28.

1A discharge or excess-pressure valve 30, urged towards its closedposition by acompressionspring 32, closes a discharge orifice 34 of thetank 116 in sucha manner thatit opens automaticallylupon a.predeterminedexcess pressure within. the tank 16 and allows they air to. escapetowards the atmosphere; while preventing any admission of air towardsthe'tank 16.

The suction or intake conduit 35 of the compressor 20 is connected to athree-way valve or pneumatic relay 36 comprising a valve member '37which cooperates with two stationary valve seats 38 and 39 in order toestablish a selective communication on the An object of the invention isto provide an economione hand between the conduit 35 and the inside ofthe low-pressure enclosure 16, by means of a passage 42 when it isapplied against the seat 39 and on the other hand between the conduit 35and the atmosphere, via tube 40 provided with an air-drying filter 41,when it is applied against the seat-38. A compression spring 43 biasesthe valve towards said second position (lefthand position) and anelectrically operated pilot valve 44, the coil 45 of which may beexcited by a source of current 46 by means of a pressure contact 47sensitive to the pressure in the enclosure 16, makes it possible toadmit compressed air of high pressure coming from the tank 28 through aconduit 48 behind a diaphragm 49 in order to bring the valve 37 to itsfirst (righthand) position, which is its position of normal operation.

3 Exhaust valves 54, 56, shown schematically and associated with thearc-extinguishing chambers 10, 12, respectively, discharge into a space58 which communicates hermetically with the inside of the hollowinsulator 14. The space 58, the hollow insulator 14 and the housing 16constitute a low-pressure enclosure for the recovery of the air escapingfrom the chambers 10, 12 through the valves 54 and 56. The recoveryenclosure is adapted to communicate I with the ambient atmosphere onlythroughthe discharge valve 30.

The compressed-air circuit interrupter in accordance with the inventionoperates in the following manner:

' At the start, the valve 37, under the action of the spring 43, is inits second position of rest shown in the drawing. The starting of thevcompressor-20 (which is driven in a conventional manner which does notform part of the present invention) causes the tank 28 and chambers and12 to be placed under high pressure (for instance 15 bars) via the tube18, the compressor taking air in through the tubes 35 and 40 from theoutside atmosphere, the air drawn in being dried by the filter 4.1. Whenthe desired high pressure is reached, the compressor stops. Thelow-pressure enclosure 58, 14 and 16 is also placed under pressureeither independently or after. an operation of the exhaust valves 54 and56. As soon 'as the pressure in said enclosure 58, 14, 16 reaches apredetermined value which may be of the order of 4 bars, the manostat47, which is set at this value, closes and excites the coil 45 ofthepilot valve 44 which opens, admitting the pressure from the tank 28through the conduit 48 behind the diaphragm 49. The valve 37 thenimmediately moves towards its first position of rest, coming against theseat 39, separating the enclosure 16- from the open air and establishingcommunication between the intake conduit 35 and the inside of theenclosure 16. Upon' the subsequent operation of the compressor, inparticular after an opening operation of the circuit interrupterresulting in a drop of pressure .in the tank 28, the compressorreestablishes the high pressure in said tank 28, taking air only fromthe enclosure 16. The pressure normally prevailing in the enclosure 16,that is to say, during the normal operation of the circuit interrupter,is not sufficiently high to open the valve 30 nor sufiiciently low toopen the contacts 47 so that the valve 44 remains normally open and thevalve 36 remains in its righthand position (not shown in the figure).

During an operation of the circuit interrupter, the high-pressure airadmitted into the arc-extinguishing chambers 10, 12 and serving, interalia, for the blowing of the arcs escapes through the valves 54, 56 andis collected in the low-pressure enclosure 58, 16, causing therein anormal increase in the pressure which is insufficient to open thedischarge valve 30. The high-pressure air supplied to the chambers 1.0,12 is taken by the conduit 18 from the high-pressure tank 28 and causestherein a drop in pressure which is sufi'rcient to cause the operationof the compressor which may, for instance, be governed by amanostat (notshown). The compressor 20 takes air in from the enclosure 16 and againfeeds the high-pressure tank 28 through the airdrying filter 26 so as.to re-establish therein the nominal high pressure which causes thestopping of the compressor. It is easy to see that the air circulates inclosed cycle, the expanded air which escapes from the arc- 4extinguishing. chambers 10, 12 being taken up again by the compressor 20and returned via the conduit 18 into the chambers l0, 12. The air uponeach cycle passes through the drying device 26 which eliminates themoisture from it, if there subsists any. v

I In normal operation, the drying products of the filter .26 are nolonger called upon to actas soon as the volume of air included dried.

In the case of a leakage from the closed circuit towards the outsideenvironment, the quantity of gas included in this system decreases andthe drop of pressure in the enclosure 16 resulting therefrom causes thein the closed circuit has been opening of. the contacts 47 as soon asthe pressure drops belowthe set value of this manostat and thus theclosing of the pilot valve 44 which causes the valve 36 to move towardsthe position shown in the drawing. Upon the subsequent operation of thecompressor 20, an amount of air necessary for the proper operation ofthe device is drawn inby the compressor via the conduits 35, 40 anddried by passage through the filterv 41 and through the filter 26. Thequantity of air to be dried is equivalent to the leaks and therefore hasnothing in common with those used in the conventional circuitinterrupters which' evacuate all the expanded exhaust air to theatmosphere. After restoring of the pressure in tank 16 to the normaloperating pressure, the contacts of the manostat 47 close and re-openpilot valve 44.

A substantial leak of the high-pressure region towards the low-pressureregion can cause a relative excess pressure in the enclosure 16 and theopening of the safety valve 30. This discharge of dry air has the sameconsequences as the said accidental leaks, specifically a decrease inthequantity of air in the closed circuit which is compensated for uponthe operation of the compressor 20 by an admission of air through theconduit 40. A slight internal leak will have no effect on the airdryingdevices, the dry air which escapes from the high pressure beingautomatically recovered in the enclosure 16 and therefore kept in thenormal circulation circuit. The only effect is a more frequent operationof the compressor. v

FIG. 2 shows another embodiment in which parts identical or similar tothose in FIG. 1 have been designated by the same reference numbers.

In this embodiment, the housing l6' freely communicates with theatmospheric air, for instance through grids 62, the low-pressure tankbeing now separate from said housing and spaced from the high-pressure.

tank 28. The inside of the support insulator 14 commu nicates with thetank 60 via a conduit 64 and the manometric switch 47 and the dischargevalve 30 are now, of course, associated with this tank 60 whichcommunicates with the valve 36 via a conduit 66 (corresponding to thepassage 42 of FIG. 1). The conduit 40 discharges within the housing 16and the operation of this device is identical to that of the device ofFIG. 1, except for the different arrangement in space of the differentparts.

What is claimed is:

1. A closed cycle double pressure compressed-air electric apparatusdisposed in atmospheric air, comprising a high-pressure compressed-airenclosure, a low-pressure compressed-air enclosure carrying compressedair having a pressure greater than the I atmospheric pressure, conduitmeans connecting said high-pressure compressed-air enclosure to theatmosphere, air-drying means inserted in said conduit means, compressormeans in said conduit means, and pressure'responsive three-way valvemeans inserted in said conduit means between said compressor means andthe atmosphere and also connected to said lowpressure compressed airenclosure, said three-way valve means being responsive to the pressureof said low-pressure compressed air enclosure and adapted to closure andto the atmosphere upon an abnormal drop of pressure therein below apredetermined pressure greater than the atmospheric pressure, andair-drying means to dry the air taken by said compressor from the air tosaid arc-extinguishing means, a low-pressure tank connect saidcompressor means selectively to said lowpressure compressed airenclosure and to the atmosphere in a manner such that said compressormeans is normally connected to said low-pressure compressed airenclosure whereby an abnormal pressure drop in said low-pressureenclosure causes said valve means to connect said compressor means tothe atmosphere.

2. A closed cycle double pressure compressed air electric apparatusdisposed in atmospheric air, comprising a high-pressure compressed airenclosure, a low-pressure compressed air enclosure, a compressor havinga high pressure outlet connected to said high pressure enclosure and aninlet, valve means connected to said inlet and adapted to connect saidinlet selectively to said low-pressure enclosure and to the atmosphere,said valve means comprising pressure sensitive control means responsiveto the pressure in said low-pressure enclosure to control the positionof said valve means in a manner such that said valve means connect saidinlet to said low-pressure enclosure under normal pressurized conditionof said low-pressure encollecting exhaust air from saidarc-extinguishing means, a compressor adapted to supply high-pressurizedair to said high-pressure tank and to maintain the pressure therein at apredetermined value, said compressor having an inlet, valve meansconnected to said inlet and also to said low-pressure tank and to theatmosphere to cause said inlet to communicate selectively with said lowpressure tank and with the atmosphere, said valve means comprisingpressure-sensitive control means for controlling the position of saidvalve means responsive-to the value of the pressure in said low-pressuretank so that said inlet is connected to said low-pressure tank undernormal pressurized condition thereof and to atmosphere upon a drop ofsaid value of the pressure in said low pressure tank below apredetermined pressure value greater than the atmospheric pressure tocause said compressor to take air from the atmosphere until said normalpressurized condition is restored, and air-drying means to dry the airtaken by said compressor from the atmosphere.

1. A closed cycle double pressure compressed-air electric apparatusdisposed in atmospheric air, comprising a high-pressure compressed-airenclosure, a low-pressure compressed-air enclosure carrying compressedair having a pressure greater than the atmospheric pressure, conduitmeans connecting said high-pressure compressed-air enclosure to theatmosphere, air-drying means inserted in said conduit means, compressormeans in said conduit means, and pressure responsive three-way valvemeans inserted in said conduit means between said compressor means andthe atmosphere and also connected to said low-pressure compressed airenclosure, said three-way valve means being responsive to the pressureof said low-pressure compressed air enclosure and adapted to connectsaid compressor means selectively to said lowpressure compressed airenclosure and to the atmosphere in a manner such that said compressormeans is normally connected to said low-pressure compressed airenclosure whereby an abnormal pressure drop in said low-pressureenclosure causes said valve means to connect said compressor means tothe atmosphere.
 2. A closed cycle double pressure compressed airelectric apparatus disposed in atmospheric air, comprising ahigh-pressure compressed air enclosure, a low-pressure compressed airenclosure, a compressor having a high pressure outlet connected to saidhigh-pressure enclosure and an inlet, valve means connected to saidinlet and adapted to connect said inlet selectively to said low-pressureenclosure and to the atmosphere, said valve means comprising pressuresensitive control means responsive to the pressure in said low-pressureenclosure to control the position of said valve means in a manner suchthat said valve means connect said inlet to said low-pressure enclosureunder normal pressurized condition of said low-pressure enclosure and tothe atmosphere upon an abnormal drop of pressure therein below apredetermined pressure greater than the atmospheric pressure, andair-drying means to dry the air taken by said compressor from theatmosphere.
 3. A substantially closed-cycle air blast circuitinterrupted comprising arc-extinguishing means, a high-pressure tanksupplying high-pressurized compressed air to said arc-extinguishingmeans, a low-pressure tank collecting exhaust air from saidarc-extinguishing means, a compressor adapted to supply high-pressurizedair to said high-pressure tank and to maintain the pressure therein at apredetermined value, said compressor having an inlet, valve meansconnected to said inlet and also to said low-pressure tank and to theatmosphere to cause said inlet to communicate selectively with said lowpressure tank and with the atmosphere, said valve means comprisingpressure-sensitive control means for controlling the position of saidvalve means responsive to the value of the pressure in said low-pressuretank so that said inlet is connected to said low-pressure tank undernormal pressurized condition thereof and to atmosphere upon a drop ofsaid value of the pressure in said low pressure tank below apredetermined pressure value greater than the atmospheric pressure tocause said compressor to take air from the atmosphere until said normalpressurized condition is restored, and air-drying means to dry the airtaken by said compressor from the atmosphere.